Auto injector with changing anchor locations for a mechanical driver

ABSTRACT

The present invention relates to a disposable auto injector that can be safely operated for automatic injection of a dose of medication and having a housing for accommodation of a syringe with a needle, the syringe being movably positioned in the housing between a first position in which position the needle is accommodated inside the housing and a second position in which position the needle protrudes outside the housing, a mechanical driver anchored to the housing at a first anchor location for applying a force to the syringe thereby moving the syringe from the first position to the second position, and wherein the mechanical driver is also configured for applying a force to the syringe by anchoring the mechanical driver to a different second anchor location.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the national phase under 35 U.S.C. 371 of PCTInternational Application No. PCT/DK2008/000400 which has aninternational filing date of Nov. 12, 2008, and also claims priorityunder 35 U.S.C. 119 to Danish application PA 2007 01596 filed on Nov.12, 2007, to U.S. provisional application 60/996,344 filed on Nov. 13,2007, to Danish application PA 2007 01867 filed on Dec. 21, 2007, toDanish application PA 2007 01869 filed on Dec. 21, 2007, and to Danishapplication PA 2007 01870 filed on Dec. 21, 2007, which applications arehereby incorporated by reference in their entirety for all purposes asif fully set forth herein.

The present invention relates to a disposable auto injector that can besafely operated for automatic injection of a dose of medication.

EP 1 349 590 discloses an auto injector with a housing that accommodatesa syringe with a needle and has a needle cover surrounding the needle.Further, the housing accommodates spring means capable of, uponactivation, pushing the needle through the needle cover as well asinjecting the dose of medication. The auto injector further has firstlocking means capable of locking the spring means in a compressed state,and first activating means capable of upon manual operation, releasingthe spring means for injection. The first activating means can not beoperated unless a contact part of the injector is actually pressedagainst the injection site. Thus, it is required to perform a two-stepoperation in order to inject the medication whereby inadvertenttriggering of the auto injector is avoided.

In other prior art auto injectors, the syringe with the needle isretracted into the housing so that the needle does not protrude from thehousing upon removal of the injector from the injection site. For thispurpose, prior art devices typically comprise two coil springs, a firstspring for moving the syringe to a position wherein the needle protrudesfrom the housing, and a second spring for retracting the syringe withthe needle into the housing. The second spring must be sufficientlystrong to overcome the force of the first spring.

Thus, there is a need for an alternative design of an auto injector.

According to the present invention, the above-mentioned and otherobjects are fulfilled by provision of an auto injector with a housingfor accommodation of

a syringe with a needle, the syringe being movably positioned in thehousing between a first position in which position the needle isaccommodated inside the housing and a second position in which positionthe needle protrudes outside the housing,

a mechanical driver anchored to the housing at a first anchor locationfor applying a force to the syringe thereby moving the syringe from thefirst position to the second position,

characterized in that

the mechanical driver is also configured for applying a force to thesyringe by anchoring the mechanical driver to a different second anchorlocation.

In one embodiment, the mechanical driver is configured for moving thesyringe from the second position to a retracted position in whichposition the needle is accommodated inside the housing, when themechanical driver is anchored to the second anchor location.

Utilisation of a single mechanical driver for moving the syringe in aforward direction from its first position to its second position andalso for moving the syringe in the opposite direction from its secondposition to its retracted position provides a simple drive mechanism forretraction of the syringe into the housing after the injection isprovided.

The mechanical driver may be positioned laterally in relation to thesyringe.

Alternatively, the mechanical driver may be arranged in an end to endrelationship with the syringe, for example with a coil spring extendingalong the longitudinal axis of the syringe.

The mechanical driver may be arranged in a coaxial relationship with thesyringe, for example such that components of the injector are arrangedboth inside a coil spring constituting the mechanical driver and outsidethe coil spring for provision of a compact construction.

The auto injector may further comprise a rotatable release shaftrotatably mounted in the housing between at least two angular positions,preferably between at least three angular positions, for control of thesequence of operation of the auto injector.

The auto injector may further comprise a first injection lock that isconfigured in a locked state for preventing syringe movement from thefirst position to the second position and an injection trigger member isconfigured for releasing the first injection lock to an unlocked stateby user operation of the injection trigger member in which unlockedstate the first injection lock does not prevent the driver from movingthe syringe from the first position to the second position.

Advantageously, the first injection lock may comprise the rotatablerelease shaft mounted in the housing for rotation between a firstangular position in which position movement of the syringe from thefirst position to the second position is prevented and a second angularposition in which position movement of the syringe from the firstposition to the second position is not prevented.

Utilization of a rotatable shaft for controlling displacement of partsin the injector by locking the position of specific parts in one angularposition of the shaft and unlocking the position of the specific partsin another angular position of the shaft makes the device more resistantto possible user dropping of the device.

In prior art devices, locking and unlocking displacement of parts in theauto injector by linear movement of locking parts is inherentlysensitive to dropping of the device, since such dropping may induce alinear movement of parts in the device, e.g. causing inadvertenttriggering of the device. In the auto injector according to theinvention, dropping of the device will not turn the rotatable shaft, andsince the auto injector can not be dropped on the injection triggermember and the release member simultaneously, the device will notinadvertently be triggered by dropping of the device.

Preferably, the rotatable release shaft is positioned laterally inrelation to the syringe.

The mechanical driver may be a spring, such as a coil spring, a constantforce spring, etc.

The spring may be arranged coaxially with the rotatable release shaftfor further size reduction of the injector.

In an embodiment of the present invention, the injection trigger memberis coupled to the rotatable release shaft and configured to turn therelease shaft from the first angular position to the second angularposition by user operation.

For example, the injection trigger member may have a flange that abuts atap protruding from the release shaft perpendicular to the longitudinalaxis of the release shaft in such a way that movement of the injectiontrigger member with the flange displaces the tap thereby turning therelease shaft an angle from the first angular position to the secondangular position.

The injector may further comprise a movable member configured with afirst ring positioned in such a way that the release shaft extendsthrough the first ring, and wherein the release shaft has first tonguesprotruding from the release shaft and extending in parallel with thelongitudinal axis of the release shaft with end edges abutting the firstring in one angular position of the release shaft thereby preventing thefirst ring from moving in the direction of the first tongues.

The first ring may have through-going grooves in its inner circularcircumferential surface abutting the release shaft positioned in such away that the first tongues of the release shaft in another angularposition of the release shaft fit respective through-going grooves inthe inner circular circumferential surface of the first ring, thegrooves being sized to accommodate the tongues thereby allowing thefirst ring to slide along the release shaft with the tongues sliding inthe grooves so that the first ring can be displaced in the direction ofthe first tongues.

The movable member may comprise a first arm connected to the first ringfor conveying a force from the driver to the syringe plunger end formoving the syringe from the first position to the second position.

For example, in the first angular position of the release shaft, thedriver may urge the first ring against the edges of the first tonguewhereby the syringe is kept in its first position, while in the secondangular position, the first tongues fit respective through-going groovesin the first ring so that the first ring is allowed to slide along therelease shaft driven by the driver whereby the syringe is moved to itssecond position.

Preferably, the driver is further configured for pushing the syringeplunger further into the syringe thereby supplying a dose of medicamentcontained in the syringe.

In the housing of the auto injector, two parts are laterally positionedin relation to each other when they are positioned by the side of eachother. For example, two elongated parts, each of which extends along alongitudinal axis, are laterally positioned in relation to each otherwhen their individual longitudinal axes do not coincide.

The lateral arrangement of the syringe with relation to the driver andthe rotatable release shaft makes it possible to mount the syringe inthe device at various selected stages of assembly of the auto injector.For example, it is possible to assemble the auto injector at one siteand subsequently mount the syringe with the medicament at another sitewhich again makes it possible for a pharmaceutical company to buy anassembled auto injector for use with their own syringe with medicamentso that handling of the syringe with medicament is kept within thepremises of the pharmaceutical company.

Further, the lateral arrangement leads to the advantage that space isavailable in the housing of the auto injector for accommodation ofdrivers of various sizes and shapes and thus, different models of theauto injector fulfilling different requirements may be provided withlimited effort.

For example, in an embodiment with a coil spring driver, coil springs ofdifferent thickness and number of turns and shape, e.g. conical coilsprings, etc, may be arranged in the housing of the auto injector forprovision of different forces, displacements, and forces varying as apredetermined function of time, etc, suitable for different types ofinjections.

In a prior art injector, components of the injector are arranged bothinside the coil spring and outside the coil spring so that geometricaldimensions of the coil spring can not easily be changed in order toobtain another force and/or displacement by the coil. The lateralarrangement according to the invention makes it possible to utilizedrivers of different geometries.

The auto injector may further be configured for user operation in acertain sequence in which triggering of an injection is only possiblefor example when the injector is pressed against the injection site.

Thus, the auto injector may further comprise a second injection lockconfigured in a locked state for preventing syringe movement from thefirst position to the second position by user operation of the injectiontrigger member and a release member configured for releasing the secondinjection lock to an unlocked state by first user operation of therelease member in which unlocked state the second injection lock doesnot prevent syringe movement from the first position to the secondposition by user operation of the injection trigger member.

The release member may be configured for abutment with the injectionsite during use, and first user operation may be constituted by the userpressing the release member against the injection site.

The second injection lock may be configured in the locked state toprevent user operation of the injection trigger member.

The auto injector may further be configured for automatically retractingthe needle back into the housing upon termination of injection ofmedication, for example immediately upon removal of the auto injectorfrom the injection site, in order to avoid inadvertent contact with theused needle.

Thus, the auto injector may further comprise a retraction lock forprevention of retraction of the syringe in a locked state.

The release member may further be configured for releasing theretraction lock to an unlocked state by second user operation of therelease member thereby allowing the driver to retract the syringe.

The second user operation of the release member may be constituted bythe user removing the release member from the injection site.

The driver may further be configured for retracting the syringe from thesecond position to a retracted position in which the needle does notprotrude from the housing.

The release shaft may further be configured for rotation between a thirdangular position in which position the shaft prevents movement of thesyringe from the second position to the retracted position and a fourthangular position in which position the shaft does not prevent movementof the syringe from the second position to the retracted position.

The release shaft may further have second tongues protruding from therelease shaft and extending in parallel with the longitudinal axis ofthe release shaft and displaced along the longitudinal axis of therelease shaft in relation to the first tongues with end edges abutting asecond ring in the other angular position of the release shaft therebypreventing the second ring from moving in the direction of the secondtongues. Thus, the end edges of the tongues abutting the second ringform the first anchor location. Through-going grooves of the second ringfit respective second tongues in a third angular position of the releaseshaft and the grooves are sized to accommodate the second tonguesthereby allowing the second ring to slide along the release shaft withthe second tongues sliding in the grooves so that the second ring can bedisplaced in the direction of the second tongues.

The third angular position may be identical to the second angularposition.

The auto injector may further comprise a second arm connected to thesecond ring for conveying a force from the driver to the syringeshoulder for retracting the syringe from the second position to theretracted position.

The above and other features and advantages of the present inventionwill become readily apparent to those skilled in the art by thefollowing detailed description of exemplary embodiments thereof withreference to the attached drawings, in which:

FIG. 1 shows an auto injector according to the invention with aprotection cap,

FIG. 2 shows the auto injector of FIG. 1 in a state ready for use andwith a part of the housing cut away,

FIG. 3 shows the auto injector of FIG. 2 with the protection capremoved,

FIG. 4 shows the auto injector of FIG. 2 with the release memberactivated,

FIG. 5 shows the auto injector of FIG. 2 with the injection triggermember activated,

FIG. 6 shows the auto injector of FIG. 2 with the syringe moved to itssecond position,

FIG. 7 shows the auto injector of FIG. 2 with the syringe emptied,

FIG. 8 shows the auto injector of FIG. 2 with the release memberreleased,

FIG. 9 shows the auto injector of FIG. 2 with the retraction lockreleased,

FIG. 10 shows the auto injector of FIG. 2 with the syringe retracted,

FIG. 11 shows an auto injector according to the invention with aprotection cap,

FIG. 12 shows the auto injector of FIG. 11 in a state ready for use andwith a part of the housing cut away,

FIG. 13 shows the auto injector of FIG. 12 with the protection capremoved,

FIG. 14 shows the auto injector of FIG. 12 with the release memberactivated,

FIG. 15 shows the auto injector of FIG. 12 with the injection triggermember activated,

FIG. 16 shows the auto injector of FIG. 12 with the syringe moved to itssecond position,

FIG. 17 shows the auto injector of FIG. 12 with the syringe emptied,

FIG. 18 shows the auto injector of FIG. 12 with the release memberreleased,

FIG. 19 shows the auto injector of FIG. 12 with the retraction lockreleased, and

FIG. 20 shows the auto injector of FIG. 12 with the syringe retracted.

The figures are schematic and simplified for clarity, and they merelyshow details, which are essential to the understanding of the invention,while other details have been left out. Throughout, the same referencenumerals are used for identical or corresponding parts.

It should be noted that in addition to the exemplary embodiments of theinvention shown in the accompanying drawings, the invention may beembodied in different forms and should not be construed as limited tothe embodiments set forth herein. Rather, these embodiments are providedso that this disclosure will be thorough and complete, and will fullyconvey the concept of the invention to those skilled in the art.

FIG. 1 shows an auto injector 10 according to the present invention. Ithas an elongated housing 12 with a substantially rectangularcross-section for an easy grip by hand. The illustrated embodiment mayfor example have a length of 10 cm, a width of 3 cm, and a thickness of1.5 cm. The housing 12 has an opening at one end thereof closed by aremovable protection cap 14. At the opposite end of the housing is atrigger button 16 that serves as the injection trigger member as furtherexplained below.

FIG. 2 shows the auto injector of FIG. 1 with a top part of the housing12 removed. The housing 12 accommodates a syringe 18 with a needle 20(not visible). The syringe 18 is positioned in a first position with theneedle 20 accommodated within the walls of the housing 12.

In the illustrated embodiment, a coil spring 22 serves as the driver formoving the syringe 18 from the first position, in which position theneedle is accommodated inside the housing, to a second position in whichposition the needle protrudes outside the housing. The coil spring 22 ispositioned laterally in relation to the syringe 18 and is compressed sothat it applies a force between a first arm, i.e. the plunger arm 24,and a second arm, i.e. the shoulder arm 26. One end of the plunger arm24 abuts the end 28 of the plunger 30 of the syringe 18 while the otherend is configured with a first ring 32. A rotatably mounted releaseshaft 34 extends through the first ring 32. Protrusions or tongues 36protruding from the release shaft 34 and extending in parallel with thelongitudinal axis of the release shaft 34 have end edges abutting thefirst ring 32 and preventing the ring from moving to the left in FIG. 2in response to the force exerted by the coil spring 22. Likewise, oneend of the shoulder arm 26 is configured with a second ring 38. Therelease shaft 34 also extends through the second ring 38. Otherprotrusions or tongues 40 protruding from the release shaft 34 andextending in parallel with the longitudinal axis of the release shaft 34have end edges abutting the second ring 38 and preventing the secondring 38 from moving to the right in FIG. 2 in response to the forceexerted by the coil spring 22. Thus, the end edges of the tongues 40abutting the second ring 38 form the first anchor location 39.

In FIG. 3, the protection cap 14 has been removed from the auto injector10 thereby exposing a skin contact button 42 intended to be pressedagainst the injection site during use and serving as the release memberas will be further explained below.

Typically, the syringe 18 also has a rubber cap (not shown) forprotection of the needle 20 in which case the protection cap 14 hasfingers gripping an edge of the rubber cap so that the rubber cap isremoved together with the protection cap 14.

A lock arm 44 has an end that abuts the trigger button 16 so that theuser is prevented from depressing the trigger button and thus, fromstarting automatic injection.

FIG. 4 shows the auto injector 10 with the skin contact button 42depressed whereby the lock arm 44 is released so that it is no longerkept in a fixed position by the pivotally mounted locking member 46.Depression of the trigger button 16 is now possible. Thus, in accordancewith the invention, the auto-injector has a second injection lockconfigured in a locked state for preventing syringe movement from thefirst position to the second position by user operation of the injectiontrigger member and a release member configured for releasing the secondinjection lock to an unlocked state by first user operation of therelease member in which unlocked state the second injection lock doesnot prevent syringe movement from the first position to the secondposition by user operation of the injection trigger member. In theillustrated example, first user operation of the release member isconstituted by the user pressing the release member against the skinsurface at the injection site.

In the illustrated embodiment, the second injection lock comprises thelock arm 44 and the pivotally mounted locking member 46. In the lockedstate shown in FIG. 3, the second injection lock prevents user operationof the injection trigger member, i.e. the trigger button 16 in theillustrated embodiment, thereby preventing syringe movement from thefirst position to the second position by user operation of the triggerbutton 16. The release member, i.e. the skin contact button 42 in theillustrated embodiment, when pressed against the injection site,releases the second injection lock to an unlocked state allowingdepression of the trigger button 16 by turning the locking member 46 sothat one end thereof abutting an end of the lock arm 44 moves away fromthe lock arm so that the lock arm 44 can be displaced together withtogether with the trigger button 16, and thus, no longer prevents thetrigger button 16 from being depressed.

FIG. 5 shows the auto injector 10 with both the skin contact button 42and the trigger button 16 depressed. The trigger button 16 has aprotruding flange 48 that abuts a tap 50 protruding from the releaseshaft 34 perpendicular to its longitudinal axis. When the trigger button16 is depressed, the protruding flange 48 displaces the tap 50 therebyturning the release shaft 34 an angle of approximately 30° from a firstangular position to a second angular position. This turns the tongues 36of the release shaft 34 into second angular positions fittingcorresponding through-going grooves (not visible) inside the first ring32 of the plunger arm 24. The grooves are sized to accommodate thetongues 36 thereby allowing the ring to slide along the release shaft 34with the tongues 36 sliding inside the grooves thereby releasing theplunger arm from its fixed position so that the plunger arm 24 isdisplaced to the left in the Figures in response to the force of thecoil spring 22. The moved plunger arm 24 pushes the plunger 30 andthereby the syringe 18 towards its second position.

Thus, in accordance with the invention, the auto injector has a firstinjection lock configured in a locked state for preventing syringemovement from the first position to the second position and an injectiontrigger member configured for releasing the first injection lock to anunlocked state by user operation of the injection trigger member inwhich unlocked state the first injection lock does not prevent thedriver from moving the syringe from the first position to the secondposition.

In the illustrated embodiment, the first injection lock of theillustrated embodiment comprises the release shaft 34 with tongues 36interacting with the corresponding grooves (not visible) in the firstring 32 of the plunger arm 24. In the locked state, the release shaft 34has a first angular position in which end edges of the tongues 36 abutthe first ring 32 and prevent movement of the plunger arm 24. Depressionof the injection trigger member, i.e. the trigger button 16 in theillustrated embodiment, releases the first injection lock by the turn ofthe release shaft 34 as explained above.

FIG. 6 shows the syringe 18 in its second position wherein the shoulder52 of the syringe 18 abuts an end of the shoulder arm 26 and an internalprotrusion in the housing 12. In the second position of the syringe 18,the needle 20 is exposed through an aperture in the skin contact button42.

As shown in FIG. 7, the plunger arm 24 continues its movement while thesyringe 18 is kept in its second position whereby the syringe 18 isemptied and the medication is injected into the user. The plunger arm 24is prevented from further movement to the left by abutment with theretraction lock arm 54 which again abuts the pivotable locking member 46and a guiding protrusion 56 of the skin contact button 42.

Upon injection, the user removes the auto injector 10 from the injectionsite. During removal from the injection site, the syringe 18 isautomatically retracted from its second position so that the needle 20is withdrawn into the housing 12 and kept within the walls of thehousing 12 thereby preventing accidental contact with the needle 20.

In FIG. 8, the auto injector 10 has been removed from the injection siteand a resilient member such as a coil spring has forced the skin contactbutton 42 back to its original position shown in FIGS. 1-3. Thecorresponding displacement of the guiding protrusion 56 of the skincontact button 42 allows the pivotally mounted retraction lock arm 54 topivot away from the first ring 32 of the plunger arm 24 in response tothe force exerted by the coil spring 22 on first ring 32. Since thefirst ring 32 abuts a skew edge of the retraction lock arm 54 furthermovement of the first ring 32 to the left in the Figure is now possibleby pivoting the retraction lock arm 54 away from the first ring 32.

This is shown in FIG. 9. Pivoting the retraction lock arm 54 alsodisconnects the first ring 32 from the remaining part of the plunger arm24 so that the plunger arm 24 is free to move back to the right togetherwith the syringe 18. Simultaneous with the pivoting of the plunger arm24 and further explained below, the first ring 32 turns the releaseshaft 34 an angle whereby the shoulder arm 26 with the second ring 38 isreleased from its fixed position and since the first ring 32 is now keptin a fixed position at the second anchor location 41, the coil spring 22urges the second arm, i.e. the shoulder arm 26 with the second ring 38in the illustrated embodiment, to the right in the Figures and therebyretracts the syringe 18 by its shoulder 52 to its original firstposition constituting the retracted position of the syringe 18. In theretracted position, the needle 20 is no longer exposed to thesurroundings thereby avoiding health hazards and allowing disposal ofthe used auto injector.

Further turning of the release shaft 34 by the first ring 32 is possiblebecause the length of the tongues 36 is shorter than the displacement ofthe first ring 32 so that the grooves of the first ring 32 do notaccommodate the tongues 36 in the position shown in FIG. 7. Then, theturning of release shaft 34 is obtained in a way similar to the turningof the release shaft 34 by the trigger button 16 as previouslyexplained. Thus, the first ring 32 has an indentation with a skew edgethat displaces a second tap (not visible) protruding from the releaseshaft 34 perpendicular to its longitudinal axis during its finalmovement towards the left of FIG. 7 thereby turning the release shaft 34another 30°. This causes the tongues 40 at the right end of the releaseshaft 34 to be turned and aligned with corresponding through-goinggrooves in the second ring 38 of the shoulder arm 26. The grooves (notvisible) are sized to accommodate the tongues 40 so that movement of theshoulder arm 26 to the right of the Figure is made possible and thus,the coil spring 22 urges the shoulder arm 26 abutting the shoulder 52 ofthe syringe 18 to the right thereby retracting the syringe 18 back intoits first position as shown in FIG. 10.

Thus, in accordance with the invention, the auto injector comprises aretraction lock for prevention of retraction of the syringe in a lockedstate of the retraction lock. In the illustrated embodiment, theretraction lock comprises the locking member 46, the guiding protrusion56, the retraction lock arm 54, and the release shaft 34 with thetongues 40. The release member, i.e. the skin contact button 42 in theillustrated embodiment, is configured for releasing the retraction lockto an unlocked state by second user operation of the release member,i.e. removal of the auto injector from the injection site therebyreleasing the skin contact button 42 from its depressed position to itsoriginal position. In its original position, the guiding protrusion 56is displaced a distance from the retraction lock arm 54 so that theretraction lock arm can turn away from the first ring 32 allowingfurther movement of the first ring 32 to the left releasing the shoulderarm for movement to the right as explained above.

Upon removal of the auto injector 10 from the injection site, it is notpossible to depress the skin contact button 42 again.

It should be noted that the auto injector may be constructed for makinginjections in more than one step. For example, in a dual chambersyringe, one chamber may contain freeze-dried medicine and a secondchamber may contain liquid to be mixed with the freeze-dried medicine. Afirst actuation of the auto injector may lead to breakage of a sealbetween the first and second chambers bringing the liquid in contactwith the freeze-dried medicine and a second actuation may lead toinjection of the mixed medicine. For example, the release shaft 34 inthe illustrated embodiment may contain more than two sets of tongues tobe aligned with corresponding grooves in the respective rings 32, 38 atrespective different angular positions of the release shaft 34 therebyallowing one of the rings 32, 38 to be displaced a predetermineddistance when the release shaft 34 has a specific angular position. Thismakes it possible to use medicine without preservatives which againmakes the auto injector more user friendly because most of the paincaused by injections is caused by preservatives in the wound.

It should further be noticed that utilization of a rotatable shaft forcontrolling displacement of parts in the auto injector by locking theposition of specific parts in one angular position of the shaft andunlocking the position in another angular position of the shaft makesthe device more resistant to the user dropping the device.

In prior art devices, locking and unlocking displacement of parts in theauto injector by linear movement of locking parts is inherentlysensitive to dropping of the device, since such dropping may induce alinear movement of parts in the device, e.g. causing inadvertenttriggering of the device. In the auto injector according to theinvention, dropping of the device will not cause rotation of therotatable shaft, and since the auto injector can not be dropped on theinjection trigger member and the release member simultaneously, thedevice will not inadvertently be triggered by dropping of the device.

FIGS. 11-20 correspond to FIGS. 1-10, respectively, and illustrate theoperation of another auto injector according to the invention operatingin a way similar to the auto injector illustrated in FIGS. 1-10 andexplained above.

The invention claimed is:
 1. An auto injector with a housing foraccommodation of a syringe with a needle, the syringe being movablypositioned in the housing between a first position in which position theneedle is accommodated inside the housing and a second position in whichposition the needle protrudes outside the housing, a mechanical driveranchored to the housing at a first anchor location for applying a firstforce to the syringe thereby moving the syringe from the first positionto the second position, characterized in that the mechanical driver isalso configured for applying a second force to the syringe by anchoringthe mechanical driver to a different second anchor location, and thatthe auto injector further comprises a first arm configured for conveyingthe first force from the mechanical driver to the syringe for moving thesyringe from the first position to the second position, and a second armconfigured for conveying the second force from the mechanical driver toa syringe shoulder for retracting the syringe from the second positionto the retracted position, and wherein the mechanical driver has one endapplying the first force to the first arm and another end applying thesecond force to the second arm, and wherein the second arm is kept in afixed position during movement of the syringe from the first position tothe second position, and wherein the first arm is kept in a fixedposition during movement of the syringe from the second position to theretracted position.
 2. An auto injector according to claim 1, whereinthe mechanical driver is configured for moving the syringe from thesecond position to a retracted position in which position the needle isaccommodated inside the housing, when the mechanical driver is anchoredto the second anchor location.
 3. An auto injector according to claim 1,wherein the mechanical driver is positioned laterally with relation tothe syringe.
 4. An auto injector according to claim 1, wherein themechanical driver is a spring.
 5. An auto injector according to claim 4,wherein the mechanical driver is a coil spring.
 6. An auto injectoraccording to claim 1, further comprising a rotatable release shaftconfigured for rotation between a first angular position in whichposition the shaft prevents movement of the syringe from the firstposition to the second position and a second angular position in whichposition the shaft does not prevent movement of the syringe from thefirst position to the second position.
 7. An auto injector according toclaim 6, wherein the rotatable release shaft is positioned laterally inrelation to the syringe.
 8. An auto injector according to claim 6,wherein the mechanical driver is a coil spring that is arrangedcoaxially with the rotatable release shaft.
 9. An auto injectoraccording to claim 6, wherein an injection trigger member is coupled tothe rotatable release shaft and configured to turn the release shaftfrom the first angular position to the second angular position by useroperation.
 10. An auto injector according to claim 9, wherein theinjection trigger member has a flange that abuts a tap protruding fromthe release shaft perpendicular to the longitudinal axis of the releaseshaft in such a way that movement of the injection trigger member withthe flange displaces the tap thereby turning the release shaft an anglefrom the first angular position to the second angular position.
 11. Anauto injector according to claim 6, wherein the release shaft is furtherconfigured for rotation between a third angular position in whichposition movement of the syringe from the second position to theretracted position is prevented and a fourth angular position in whichposition movement of the syringe from the second position to theretracted position is not prevented.
 12. An auto injector according toclaim 1, wherein the first arm has a first ring positioned in such a waythat a release shaft extends through the first ring, and wherein therelease shaft has first tongues protruding from the release shaft andextending in parallel with the longitudinal axis of the release shaftwith end edges abutting the first ring in one angular position of therelease shaft thereby preventing the first ring from moving in thedirection of the first tongues in response to the force applied to thefirst arm by the mechanical driver.
 13. An auto injector according toclaim 12, wherein the first ring has through-going grooves in its innercircular circumferential surface abutting the release shaft positionedin such a way that the first tongues of the release shaft in anotherangular position of the release shaft fit respective through-goinggrooves in the inner circular circumferential surface of the first ring,the grooves being sized to accommodate the tongues thereby allowing thefirst ring to slide along the release shaft with the tongues sliding inthe grooves so that the first ring can be displaced in the direction ofthe first tongues in response to the force applied to the first arm bythe mechanical driver.
 14. An auto injector according to claim 12,wherein the second arm has a second ring positioned in such a way that arelease shaft extends through the second ring, and wherein the releaseshaft has second tongues protruding from the release shaft and extendingin parallel with the longitudinal axis of the release shaft anddisplaced along the longitudinal axis of the release shaft in relationto the first tongues and having end edges abutting the second ring inthe other angular position of the release shaft thereby preventing thesecond ring from moving in the direction of the second tongues inresponse to the force applied to the second arm by the mechanicaldriver.
 15. An auto injector according to claim 14, wherein the secondring has through-going grooves in its inner circular circumferentialsurface abutting the release shaft positioned in such a way that thesecond tongues of the release shaft in a third angular position of therelease shaft fit respective through-going grooves in the inner circularcircumferential surface of the second ring, the grooves being sized toaccommodate the second tongues thereby allowing the second ring to slidealong the release shaft with the second tongues sliding in the groovesso that the second ring can be displaced in the direction of the secondtongues in response to the force applied to the second arm by themechanical driver.